It has been the custom in the tobacco industry for some period of time to characterize the filling power of tobacco by means of procedures which determine the volume of tobacco occupied by a specific weight thereof under standard packing conditions. The greater volume of the tobacco, the less is the amount of tobacco required to fill a cigarette. Obviously, techniques for improving the filling capacity of the tobacco are desirable.
Within the past 10 years the tobacco industry has seen the commercial development of processes for expanding tobacco. These procedures generally involve rapid vaporization, solvent treatment, or both, as described, inter alia, in U.S. Pat. Nos. 2,344,106, 2,653,093, 2,739,599, 3,141,871 and 3,452,451, and Canadian Pat. No. 680,461. Some of the procedures, for example, involve rapid vaporization of liquids such as water or various organic liquids present in the interstices of the cellular structure of the tobacco. Rapid vaporization causes the cellular structure to expand and increase the filling power of the tobacco. Puffing may also be obtained by subjecting tobacco to high pressure gas or vapor and rapidly releasing that pressure.